Sound film mechanism



Oct 1940- A. G. ZIMMERMAN 2,219,731

SOUND FILM MECHANISM Filed June 28, 1938 27 if m 1/ "/A lnventor y%nomegPatented Oct. 29, 1940 UNITED STATES.

2,219,731 soUnn FILM MECHANISM Arthur G. Zimmerman, Indianapolis, Ind.,assignor to Radio Corporation of America, a. corporation of DelawareApplication June 28, 1938, Serial-No. 216,300

3 Claims.

This invention relates to sound film mechanism and pertains morespecifically to an improved type of pad roller for maintaining the filmin proper cooperative relation with a sprocket or drum adapted to carrythe film. More particularly it pertains to an improved type of springfor maintaining the said pad roller either in cooperative relation withthe sprocket or drum or in a position removed from the said sprocket ordrum.

Although specifically described as applied to a sound reproducer, theinvention is not limited to sound reproducers but may be applied to anytype of motion picture apparatus or other apparatus where a strip offlexible material is to be maintained in contact with -a supportingroller by means of pad rollers or pressure rollers, the differencebetween a pad roller and a pressure roller being that the pressureroller rests B0 firmly against the surface of the-material and causes itto engage the supporting drum at all times, whereas the pad roller issupported at a predetermined distance from the surface of the supportingdrum and 'only contacts the fili n 25 when it attempts to rise from thesurface or when, for example, a splice passes through the apparatus. a

In the application of the invention described in the followingspecification, it is used in con- 0 junction with a double pad rollerwhich serves to maintain the film in proper cooperative rela tion to theconstant speed sprocket of a sound reproducer.

The invention involves the provision of a C- 5 shaped spring having endsturned in opposite directions to serve as as bearings therefor, the saidspring being under compression at all times and being more nearly closedat the peak of movement of the arms supporting thepad roll- 0 ers thanat the extreme positions thereof.

One object of the invention is to provide an improved pad rollermechanism.

Another object of the invention is to provide an improved pressurespring for pad rollers.

Another object of the invention is to provide a pressure spring ofreadily adjustable tensio for a device of the class described.

Another object of the invention is to provide a spring which may bereadily installed or removed but which will have no tendency to jump outof place.

Other and incidental objects of my invention will be apparent to thoseskilled in the art from a reading of the following specification. and aninspection of the accompanying drawing, in which Figure 1 is a side viewof a soundhead includ ing a pad roller and spring arrangement accordingto my invention, and 5 Figure 2 is a top view partly in section of thepad roller and spring arrangement.

Referring first to Fig. 1,-the soundhead, which is constructed ingeneral accordance with Loomis et a1. Patent 2,019,147 as modified inaccordance 10 with application Serial No. 214,508, filed June 18, 1938,is provided with a casing member Ill. Supported in this casing memberare a sprocket II and a film drum I2 adapted to support a film I 3 andcarry it past the optical system H which '1 directs a fine line of lightthereupon from the exciter lamp l5. This light after passing through theportion of the film overhanging the drum I2 is directed by a prismaticlens, indicated at l6, to the photocell IT. The sprocket II is drivenfrom an appropriate source of power and pulls the film over the drum l2which is provided with a viscous damper, all as described in theaforesaid Loomis et al patent. From the sprocket H the film passesdownwardly around a double spring idler l8 to the take-up mecha-' nism,as described and claimed in my aforesaid application. The film is keptin contact with the sprocket II and is prevented from jumping off thesprocket teeth'by the pad rollers l9 and 20 0 which are carried upon thearm 2| pivoted on the screw 22. This am when in its closed positionnearest the sprocket is held spaced therefrom by the screw 23'whichcooperates with the stop 24 and in the open position, permitting film tobe threaded into the apparatus, the arm 2| rests against the pin 25.

It will be apparent that for the spring to maintain the arm 2| in thetwo positions described it must be under either tension or compressionin both end positions but must be under a greater tension or compressionat the mid-position. This has been accomplished in the prior art invarious ways. For example, one usual form of device has involved ahelical spring which pressed a ball into a notch at each of the endpositions.

In another form, a spring-pressed plunger cooperated with a properlyshaped cam carried on the arm, and many other forms of springs have beenprovided which were correspondingly complicated, expensive and requiredconsiderable machine work in their production. I avoid all thesecomplications and at thesame time secure an even superior result by theprovision of the C-shaped spring 26, one end of which is turned 2downwardly at 21 and fits into the boss 28, and

the other end of which is turned upwardly, indicated at 29, and fitsinto an appropriate hole 30 in the arm 2 I. The boss 28, or rather thehole in the middle of this boss, is located approximately on thebi-sector of the angle defined by the arm 2! in its two extremepositions, 1. e., resting against the stop 24 or against the stop pin25. The spring 26 is made of appropriate spring material and may be soshaped that when removed from the apparatus it is approximatelysemi-circular, while when in position at either end of the travel of thepad roller it is approximately C-shaped, and at the midpoint of itstravel it is somewhat more closed in form. The holes in the boss 28 andin the arm 2| are substantially perpendicular to the plane of movementof the arm 2|, while spring 26 lies in a plane parallel to the saidplane of movement. In order for the spring 26 to be moved from itsnormal position, it is necessary that it be deflected from a plane inorder to remove one end or the other of the spring from its hole and thespring, therefore, has no tendency to jump from its operative position,al-

though, it desired, the ends 21 and 29 may be tilted outwardly from eachother and: slightly away from the true perpendicular to the plane of thecurved spring.

It will be apparent that this spring is relatively easily shaped to ahigh degree of precision and that the tension thereof may be adjusted byeither opening or closing the shape of the C slightly when the spring isat rest.

Having now described my invention, I claim:

1. In combination with a roller'adapted to setion adjacent a rotary filmsupporting member or in another fixed position removed therefrom,resilient means for maintaining said pad roller in either of saidpositions, said resilient means comprising a C-shaped spring memberin asingle plane having extensions at its ends in opposite directionssubstantially perpendicular to the said plane, one of said extensionsengaging said arm and the other of said extensions engaging a fixedmember.

3. In combination with an arm supporting roller adapted to selectivelyrest against a stop in a fixed position adjacent a rotary filmsupporting member or against another stop in a fixed position removedtherefrom, resilient means for maintaining said pad roller in either ofsaid positions, said resilient means comprising a C-shaped spring memberin a single plane having extensions at its ends in opposite directionssubstantially perpendicular to the said plane, one of said extensionsengaging said arm and the other of said extensions engaging a fixedmember located approximately midway betweensaid stops.

G. ZINIMERMAN.

